This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The prevalence of Female Athlete Triad disorders in exercising women has been documented to range from 1-44% for menstrual disorders, 2-66% for disordered eating and 6 and 48% for osteoporosis and osteopenia, respectively. Bone loss in female athletes is associated with an increased risk of stress fractures and fractures of the hip and spine. The etiology of Triad disorders involves chronic energy deficiency and resulting adaptive changes, i.e., reductions in circulating metabolic hormones and resting energy expenditure, producing a hypometabolic state. Chronic energy deficiency is a well recognized factor in the suppression of reproductive function, and recently, bone loss in amenorrheic athletes has been directly linked to these metabolic changes as well, an effect independent of compromised estrogen status. Although chronic energy deficiency is well documented in female athletes with menstrual disturbances, its effects on strength, power, cardiorespiratory endurance, and specific sport performance have not been examined. Similarly, whether reversing energy deficiency will improve performance is not known. Given the negative health consequences and potential impact on performance of Female Athlete Triad disorders, studies are necessary that examine strategies to reverse these negative outcomes. Currently, there are no established guidelines for reversing energy deficiency and restoring menstrual function in amenorrheic athletes. The overall goal of this study is to examine whether the reversal of energy deficiency in amenorrheic athletes will produce significant health and performance outcomes. We will test whether 6 months of daily calorie supplementation will a) reverse energy deficiency, b) restore menstrual function, c) lead to favorable changes in biochemical markers of bone turnover, and d) be associated with significantly improved physical performance. A randomized prospective study in exercising women aged 18-35 yrs is proposed with a 2 week screening period followed by a 4 week baseline and 6 month intervention period. Screening procedures over two weeks will include hormonal and menstrual history documentation of functional hypothalamic amenorrhea, assessments of body weight and composition, diet and physical activity. Baseline procedures over four weeks will include fasting blood samples for T3, ghrelin, P1NP, 2nd morning void urine collections for uCTX, a 3-day diet log, measurement of 24 hour energy expenditure (RT3 accelerometer), assessment of body composition and bone density (DXA), and testing for muscular strength, endurance, power, cardiorespiratory endurance, and a sport specific task. Intervention subjects will then begin increasing dietary intake by 20-30% of eucaloric intake by consuming sports supplements for 6 months, while controls will maintain their usual diet. All measures will be repeated at mid and post-study points. We expect that increased dietary intake will lead to a) reversal of energy deficiency, b) restoration of menses, c) favorable changes in bone turnover, and d) significant improvement in physical performance. Data will be compared pre and post for controls and intervention subjects with ANOVA for repeated measures. If our results are positive, the information could be used to develop practical dietary guidelines for coaches, athletic trainers and athletes themselves, therefore improving health and performance in premenopausal exercising women.